Shaft and actuator for retractable snowmobile ski wheel system and method of using the same

ABSTRACT

The present invention provides a retractable wheel system for snowmobile skis. The retractable wheel system of the present invention may be installed on a snowmobile ski without affecting its structural integrity by installing the system on the reinforced portion of the snowmobile ski. When a user circulates in a path with little or no snow, the retractable wheel system is positioned in the extended configuration by the user and the system will automatically return to the retracted configuration when the user returns in a snowy zone. This is realized by using a pre-tensioned spring that will reposition the wheel in the retracted configuration. The spring transmits a rotational movement to the member on which the wheel is fixed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is a divisional application of commonlyassigned U.S. patent application Ser. No. 13/462,932, itself acontinuation application of commonly assigned U.S. patent applicationSer. No. 12/633,325, itself claiming the priority of the commonlyassigned Canadian Patent Application no. 2,647,375, entitled “Roueretractable pour ski de motoneige” and filed at the Canadian PatentOffice on Dec. 8, 2008. The present application claims the benefits ofpriority of all these prior applications. The disclosures of these priorapplications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to vehicles partially supportedby one or more skis. More specifically, this invention is related to asnowmobile having a retractable wheel to circulate in a zone with littleor no snow.

BACKGROUND OF THE INVENTION

Snowmobiles are vehicles adapted to circulate on snowy or icy surfaces.However, users often have to circulate on surface having little or nosnow. These non-snow surfaces are often made from asphalt, concrete,stony ground, for example, which are highly abrasive for theundersurface of the snowmobile ski. Prior art shows some systems inwhich the user has to install wheels on the skis to circulate onabrasive surface to prevent the undersurface of the ski to contact theabrasive surface.

Disadvantage of such system is that the manipulation to install thewheel is complex and difficult. Indeed, in many of systems provided inprior art, the user has to stop the snowmobile, get down from it andinstall manually the wheels, pass through the zone with little or nosnow, stop again the snowmobile and remove the wheels. Thesemanipulations have for consequence that the users will not install thewheel and pass through the zone with little or no snow on the ski,causing a premature wear of the ski.

Also, in snowy condition, the wheel systems may be jam with snow or ice,increasing the difficulty of the manipulation.

Finally, it is important to consider where the systems are installed onskis. Since the weight of the snowmobile is directly transmitted to theski, the latter are under high mechanical stresses. In some systems ofprior art, fixation holes are practiced in the ski, weakening the skiand causing eventually the breaking of the ski. Since the skis arereinforced where they are attached to the snowmobile, it would beadvantageous to install the wheel in this section. Indeed, if the wheelsare installed in a non-reinforced zone, the ski will bend, diminishingthe contact surface between the snow and the ski. This configurationdiminishes the performance of the ski on snow. It also causes aninadequate distribution of the weight of the snowmobile on the ski and apremature wear.

A deformation of the skis may occur if the wheel system is installed ona part of the ski that is not reinforced, causing the ski to bend underthe weight of the snowmobile. Furthermore, the wear bar usually installon the undersurface of a ski will be highly affected by such a stressand curvature. It is known that the wear bar is made from carbide havinghigh hardness and thus being highly fragile. As a consequence, the wearbar will become cracked and chipped.

SUMMARY OF THE INVENTION

The aforesaid and other objectives of the present invention are realizedby generally providing a retractable wheel system for snowmobile ski,the snowmobile ski being connected to the snowmobile with a kingpin, thekingpin being connected to the snowmobile ski through a first openingand a second opening in the ski, the system having a retractedconfiguration and an extended configuration, the extended configurationbeing actuated by a user of the snowmobile and wherein the system isconfigured to return automatically in the retracted configuration, thesystem comprising a spring having a first extremity and a secondextremity, the aid spring being pre-tensioned at a predetermined amount,a pivoting member connected to the ski and to the spring, the pivotingmember being actuated by the spring, a shaft having a first and a secondextremity, the shaft comprising a slot at the second extremity, thepivoting member being pivotally mounted along the shaft, and the whereinthe first extremity of the spring is inserted in the slot, a connector,the connector being mounted on the second extremity of the shaft, theconnector comprising a plurality of holes configured to receive secondextremity of the spring, a wheel rotatably connected to the pivotingmember; and a stopper.

In a preferred embodiment, the spring is a helical torsion spring. Inanother embodiment, the spring is of the mainspring type.

In a preferred embodiment, slot in the shaft is perpendicular to thesecond extremity of the shaft. In another embodiment, the top portionand the bottom portion of the slot of the shaft are at an angle π, theangle π preferably comprised between 10° and 14°.

In another embodiment, the present invention provides a shaft to be usedwith a spring, the spring having a first and a second extremity, theshaft comprising a slot, wherein the slot has a top portion and a bottomportion, and wherein there is an angle π between the bottom portion ofthe slot and the top portion of the slot, wherein the first extremity ofthe spring is inserted in said slot, wherein the slot forces the firstextremity of the spring towards the bottom portion of the slot when thespring is twisted to be tighter. The angle π is comprised between 10°and 14°.

The retractable wheel system of the present invention is easilyinstalled on an existing snowmobile ski. To do so, the transmission armand the kingpin of the ski are dismounted and the retractable wheelsystem is fixed to the ski using the kingpin. The retractable wheelsystem comprises a wheel, a pivoting member, a fixation member and aspring. The fixation member is fixed to the snowmobile ski using thekingpin and is secured with bolt and nut. An important feature of thepresent invention is the installation of the retractable wheel systemusing the kingpin to prevent deformation and damage of the ski.

It is to be noted that the fixation member could be omitted if the skiwas already equipped with fixation means for the pivoting member.

An advantage of the present invention is that it has little or no effecton the structural integrity of the ski compared to prior art. Indeed,the retractable wheel system of the present invention is installed onthe reinforced portion of the ski. Also, the system is secured with thekingpin thus the force distribution is almost the same as the normaluse, i.e. with the skis.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the inventionwill become more readily apparent from the following description,reference being made to the accompanying drawings in which:

FIG. 1a is an exploded view showing a first embodiment of theretractable wheel system according to the present invention, for theleft ski of a snowmobile.

FIG. 1b is an exploded view showing a first embodiment of theretractable wheel system according to the present invention, for theright ski of a snowmobile.

FIG. 2a is an exploded view of the fixation system of the embodimentshown in FIG. 1 a.

FIG. 2b is an exploded view of the fixation system of the embodimentshown in FIG. 1 b.

FIG. 3a is an exploded view of the retraction system of the embodimentshown in FIG. 1 a.

FIG. 3a is an exploded view of the retraction system of the embodimentshown in FIG. 1 b.

FIG. 4a is a partially exploded view of the retractable wheel system ofthe embodiment shown in FIG. 1 a.

FIG. 4b is a partially exploded view of the retractable wheel system ofthe embodiment shown in FIG. 1 b.

FIG. 5a is an isometric view of the retractable wheel system of theembodiment shown in FIG. 1 a.

FIG. 5b is an isometric view of the retractable wheel system of theembodiment shown in FIG. 1 b.

FIG. 6 is an isometric view showing one of the steps to mount theretractable wheel system on a snowmobile ski.

FIG. 7 is an isometric view showing one of the steps to mount theretractable wheel system on a snowmobile ski.

FIG. 8 is an isometric view showing the retractable wheel system of FIG.1 as mounted on a snowmobile ski.

FIG. 9 is an isometric exploded view showing a second embodiment of theretractable wheel system for snowmobile ski.

FIG. 10 is an isometric view showing the retractable wheel system ofFIG. 9, in a retracted configuration.

FIG. 11 is an isometric exploded view of the embodiment shown in FIG. 9.

FIG. 12 is an isometric view of the embodiment of FIG. 9 in an extendedconfiguration.

FIG. 13 is an isometric view of the embodiment of FIG. 9 in a retractedconfiguration.

FIG. 14 shows one of the steps to mount the second embodiment of theretractable wheel system on a snowmobile ski.

FIG. 15 shows another step to mount the second embodiment of theretractable wheel system on a snowmobile ski.

FIG. 16 shows another step to mount the second embodiment of theretractable wheel system on a snowmobile ski.

FIG. 17 shows another step to mount the second embodiment of theretractable wheel system on a snowmobile ski.

FIG. 18 shows another step to mount the second embodiment of theretractable wheel system on a snowmobile ski.

FIG. 19 shows another step to mount the second embodiment of theretractable wheel system on a snowmobile ski.

FIG. 20 shows another step to mount the second embodiment of theretractable wheel system on a snowmobile ski.

FIG. 21 shows another step to mount the second embodiment of theretractable wheel system on a snowmobile ski.

FIG. 22 shows another step to mount the second embodiment of theretractable wheel system on a snowmobile ski.

FIG. 23 shows another step to mount the second embodiment of theretractable wheel system on a snowmobile ski.

FIG. 24 shows another step to mount the second embodiment of theretractable wheel system on a snowmobile ski.

FIG. 25 shows another step to mount the second embodiment of theretractable wheel system on a snowmobile ski.

FIG. 26a is a side view showing a second embodiment of a shaft, to beused with the left ski of a snowmobile.

FIG. 26b is a side view showing a second embodiment of a shaft, to beused with the right ski of a snowmobile.

FIG. 26.1a is a close-up view of detail b of FIG. 26 a.

FIG. 26.1b is a close-up view of detail b of FIG. 26 b.

FIG. 26.2a is a top view of the shaft shown in FIG. 26 a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A novel retractable wheel system for snowmobile ski will be describedhereinafter. Although the invention is described in terms of specificillustrative embodiment(s), it is to be understood that theembodiment(s) described herein are by way of example only and that thescope of the invention is not intended to be limited thereby.

In FIGS. 1 to 6, the figures <<a>> are referring to the retractablewheel system of the left snowmobile ski and the figures <<b>> arereferring to the retractable wheel system of the right snowmobile ski.Since the part on left and right sides are symmetric, the same numbersare attributed to identical part of the left and right sides.

FIG. 1 shows the retractable wheel system comprising a wheel 2, apivoting member 4, a fixation member 6, and a spring 8. In thispreferred embodiment, the fixation member 6 is fixed on the snowmobileski with the kingpin 18 and the position is secured with bolts 14 andnuts 16, or other appropriate means such as bolt and nut, welding,rivets, etc. . . . The fixation member 6 comprises an opening 5configured to receive the kingpin 18. The snowmobile ski is connected tothe snowmobile with an arm 78 and the kingpin 18. The fixation member 6provides attachment means for the retractable wheel system so that thesystem may be retrofit to an existing snowmobile ski.

The spring 8, or helical torsion spring 8, is a spring that works bytorsion or twisting, it stores mechanical energy when twisted. Theamount of force or torque it exerts is proportional to the amount it istwisted or rotated on itself. To create the pretension in the spring,the latter is subjected to twisting about its longitudinal axis bysideways forces (bending moments) applied to its ends, twisting thespring tighter.

The pivoting member 4 comprises an opening 82 to receive the shaft 20,an opening 84 on which the stopper 44 is installed and an opening 86 onwhich the wheel 2 is connected. The pivoting member 4 is rotativelyconnected to the fixation member 6 with the shaft 20. The pivotingmember 4 rotates along the longitudinal axis of the shaft 20, under theforce applied by the spring 8 (to retract the system) or under a forceapplied by a user (to extend the system).

The shaft 20 comprises a first extremity 133 and a second extremity 233.The shaft 20 comprises a slot 33 at its second extremity 233. If a firstembodiment, the slot is substantially perpendicular to the secondextremity 233, as shown in FIGS. 1 to 3.

The connector 24 is a piece configured to be connected to the firstextremity 133 of the shaft 20. The connector 24 comprises a plurality ofholes 34, these holes being configured to receive the second extremity30 of the spring 8. In a preferred embodiment, the connector 24comprises eleven holes 34. In a preferred embodiment, the connector 24is screwed to the shaft 20 so that the connector 24 may be changed forreparation or to change the number of holes 34 to provide a plurality oftension levels in the spring. The connector 24 is preferably connectedto the pivoting member 4. In the preferred embodiment, the connector 24is screwed to the pivoting member 4. The connector 24 transmits therotation induced by the spring 8 to the pivoting member 4.

The adapter 12 is a hollow cylindrical part configured to receive theshaft 20. The adapter 12 comprises a groove 32 configured to receive thefirst extremity 28 of the spring 8.

The retraction system 22, composed by the spring 8 and the shaft 20, iscomprised in the case 10. The case 10 is preferably threaded at its openextremity and may be connected to the connector 24 which is alsothreaded. The connection between the case 10 and the connector 24 ispreferably leakproof.

The first extremity 28 of the spring 8 is folded so it can be insertedinto the slot 33 of the shaft 20. The second extremity 30 of the spring8 is folded to interact with the one of the holes 34 of the connector24.

To install the spring 8, the first extremity 28 is firstly inserted inthe groove 32 of the adapter 12 and the adapter 12 is installed on theshaft 20. It is to be noted that after installation, the first extremity28 of the spring 8 passes into the slot 33 and into the groove 32. Thesecond extremity 30 is then inserted in one the holes 34. To create thepretension in the spring 8, the spring 8 is rotated or twisted on itselfuntil the desired tension is reached, and the second extremity is theninserted in one of the holes 34 to maintain this pretension in thespring 8.

Retaining rings 36 and 37 are preferably inserted on the shaft 20, oneach sides of the spring 8.

The retractable wheel system comprises a stopper 44 which is fixed, inthe present embodiment, to the pivoting member 4. An o-ring 46 isinstalled to the side of the stopper 44. In a retracted configuration,the stopper 44 is in contact with the fixation member 6.

The wheel 2 is rotatably connected to the pivoting member 4 with thewheel shaft 38. The wheel 2 is mounted on a sleeve 40 and two washers 42are installed on both sides of the wheel 2, on the wheel shaft 38. Asshown in FIG. 4a , in the retracted configuration, the stopper 44contacts the fixation member. The role of the stopper 44 is to stop therotation of the pivoting member induced by the spring 8. The stopper 44also dictates the position of the wheel 2 and of the pivoting member 4in the retracted position. The tension in the spring 8 causes thepivoting member 4 to rotate counterclockwise (for the right ski) untilthe stopper 44 contacts the fixation member 6.

FIGS. 6 to 8 show how the retractable wheel system is mounted on asnowmobile ski 50. The kingpin 18 comprises a first 1802 and a secondextremity 1803, and a cavity 1801 configured to receive a fastener 60.The kingpin 18 is shaped to be inserted in the first opening 52 andsecond opening 54 of a snowmobile ski. In a preferred embodiment, thekingpin 18 is shaped as an elongated cylinder comprising a first 1802and a second extremity 1803. The second extremity 1803 of the kingpin 18comprises a threaded cavity 1801 configured to receive a compatiblethreaded fastener 60. The ski 50 usually comprises a first opening 52and a second opening 54 to receive the kingpin. Bushings 56 and 58 arepreferably inserted in the first opening 52 and second opening 54. Thekingpin 18 is then inserted in the bushing 56 and 58. The kingpin 18 isthen fixed to the ski 50, using a threaded fastener such as bolt 60. Awasher 62 is preferably installed between the bushing 54 and the bolt60. As show in FIGS. 6 and 7, the second extremity 1803 of the bodyportion of the kingpin 18 does not typically extend beyond the outerside of the opening 54 receiving the second extremity 1803.

Before using the retractable wheel system, an appropriate quantity ofprotective material and/or lubricant 91 such as synthetic oil ispreferably applied in the case 10 to lubricate the mechanism whileprotecting it from environment such as water, salt, etc. . . .

FIG. 8 shows the retractable wheel system in a retracted configuration,the wheel 2 being located at a horizontal level higher that theundersurface of the ski 50. The pivoting member 4 rotates along therotation axis 64.

It is to be noted that the shaft or kingpin that is initially used tofix the ski to the snowmobile may be used to fix the retractable wheelsystem of the present invention. It is also possible to use anothershaft conceived for the retractable wheel system.

To move the wheel 2 in an extended configuration the user pushes withhis foot on the actuator 27 in the direction indicated by the arrow 66.The user applies the adequate force to overcome the tension in thespring 8. The actuator 27 is a piece used to push downwardly the wheel 2in an extended configuration and which is easily actuated with a foot.This manipulation moves the wheel so that the bottom of the wheel 2 isat a horizontal level lower than the undersurface of the ski 50. Thewheel 2 is then in contact with the ground and is maintained in thisconfiguration because of the weight of the snowmobile, this weightcreating a force greater than the tension in the spring 8. It ispossible to adjust the distance between the bottom of the wheel 2 andthe undersurface of the ski 50, by modifying the dimensions of the partsof the system, for example. This distance may be of 1 inch or 2 inches,for example.

While the user goes back in a snowy zone, the non-snowy surface isgradually or suddenly replaced by a snowy surface. When there is enoughsnow under the ski 50, i.e. more than the distance between the ski 50and the bottom of the wheel 2, the tension in the spring 8 will causethe wheel to go back in a retracted configuration. The tension in thespring 8 has to be adjusted to bring back the wheel in a retractedconfiguration. It is possible to adjust the tension according to theshow condition. For example, if the snow is dense or hard, it ispossible to adjust the spring 8 to obtain a higher retraction force toinsure that the wheel will go back in a retracted configuration.

FIGS. 9 to 25 show a second embodiment of the retractable wheel systemaccording to the present invention. The retractable wheel systemcomprises a fixation member 106, a pivoting member 104, a wheel 102 anda retraction system 122. The fixation member 106 is fixed to thesnowmobile ski 150 with attachment means, such as bolt 114 and nut 116.The bushing 156 is inserted in the opening 152 of the ski and in theopening 151 of the fixation member 106. As shown in FIG. 9, the bushing156 is preferably fixed to the fixation member 106. This configurationallows the distribution of the forces in the reinforced portion of theski and preserves the structural integrity of the ski 150. It has beenfound in experimentation that the kingpin is more subject to deformationwithout the use of the bushing 156. The bushing 156 may have anhexagonal head improving the tightening between the side of thesnowmobile ski 150 and the fixation member 106.

In this second embodiment, the spring 108 is of mainspring type. Amainspring is typically a spiral spring of metal ribbon. Winding, ortwisting the spiral tighter, stores energy in the mainspring. Also, inthis second embodiment, the kingpin comprises a kingpin member 182 whichcomprises a body portion. The body portion comprises a first and asecond extremity, a head portion located at the first extremity and athreaded portion located on the outer surface of the body portion. Thekingpin also comprises a bushing 156. The bushing 156 comprises a hollowbody portion having a first and a second extremity, a head portionlocated at the first extremity of the bushing 156 and a threaded portion117 located on the outer surface of the body portion adjacent to thesecond extremity of the bushing 156. Furthermore, the second extremityof the bushing 156 typically does not extend beyond the outer side ofthe first opening. In addition, the kingpin generally comprises asecuring member 144. The securing member 144 comprises a threaded bodyand a head located at one extremity of the threaded body 117. Thekingpin member 182 of the kingpin is typically received through thehollow body portion of the bushing 156, wherein the second extremity ofthe kingpin is secured by the securing member 144 and wherein thekingpin member 182 is configured to be inserted through a first openingin the snowmobile ski 150. The securing member 144 typically comprises ahollow body. The inner surface of the hollow body of the securing member144 is threaded and the hollow body of the securing member 144 isconfigured to receive the compatible threaded portion of the kingpinmember 182.

The pivoting member 104 is rotatably connected to the fixation member106 with the shaft 118. In this embodiment, the shaft 118 is screwed tothe fixation member 106 and allows the pivoting member 106 to rotatealong the shaft 118. The wheel 102 is rotatably fixed to the pivotingmember 104 with the wheel shaft 188. A washer 142 is installed betweenthe wheel 102 and the bolt head of the wheel shaft 188.

The case 180 comprises the spring 108. The spring 108 is an elongatedstrip made from a resilient material having rigidity, such as steel forexample, that is rolled on itself. The case 180 comprises an opening 181configured to received the cylindrical part 186. The spring 108comprises a first hook 194 and a second hook 196. The first hook 194 isretained by the slot 197 of the cylindrical part 186. The second hook isretained by the extension 198 extending from the fixation member. Thetension in the spring is adjusted by modifying the number of loops ofthe strip. To obtain a higher tension in the spring, the spring isrotate to create more loops.

The hooks 194 and 196 are a folded portion of the strip allowing thespring 108 to be retained by the slot 197 and the extension 198. It isto be noted that the strip could be retained otherwise, with asupplementary part for example or by using other appropriate means.

A stopper 144, also previously referred to as a securing member, isconnected, screwed in this preferred embodiment, to the extremity of thebushing 156 extending on the other side of the fixation member 106. Thestopper 144 allows the securing of the kingpin 182 holding the arm ofthe ski. An o-ring 146 is preferably installed on the stopper 144. Asshown more specifically in FIG. 10, the pivoting member 104 comprises anextension 192 forming an arcuate portion 190. The arcuate portion isconfigured to mates the stopper 144 and the o-ring 146. The stopper 144could be installed elsewhere on the system, for example on the fixationmember, without departing from the scope of the present invention.

The spring 108 is maintained in a compressed state by retaining itsextremities in the slot and the extension, creating a rotational forceon the pivoting member 104. This rotational force allows the wheel tostay in a retracted configuration as shown in FIG. 13, and allows thewheel to return automatically from the extended configuration to theretracted configuration when the snowmobile returns on a snowy zone.

To move the wheel 102 in an extended configuration prior to circulate inan non-snowy zone or lightly snowy zone, the use pushes on the pivotingmember to move the wheel 102 in an extended configuration as shown inFIG. 12. The user applies a force sufficient to overcome the tension ofthe spring. This will position bottom part the wheel 102 at a horizontallevel lower than the undersurface of the ski 150. The wheel is then incontact with the ground and is maintained in this configuration underthe weight of the snowmobile. It is possible to adjust the distancebetween the bottom of the wheel 2 and the undersurface of the ski 50, byusing pieces having different dimension, for example. This distance maybe of 1 inch or 2 inches, for example.

While the user goes back in a snowy zone, the non-snowy surface isgradually or suddenly replaced by a snowy surface. When there is enoughsnow under the ski 150, i.e. more than the distance between the ski 150and the bottom of the wheel 102, the tension in the spring 108 willcause the wheel to go back in a retracted configuration. The tension inthe spring 108 has to be adjusted to bring back the wheel in a retractedconfiguration. It is possible to adjust the tension according to theshow condition. For example, if the snow is dense or hard, it ispossible to adjust the tension in the spring 108 to obtain a higherretraction force to insure that the wheel will go back in a retractedconfiguration.

Referring now to FIGS. 14 to 25, to install the retractable wheelsystem, the kingpin 182 of the snowmobile ski and the arm 178 aredismounted from the ski and the piece 184 is removed. The bushing 156 isinstalled where the piece 184 has been removed. The kingpin 182 is theinserted through the arm 178 and through the installed bushing 156,thereby mounting the arm 178 to the snowmobile ski. The retractablewheel system 100 is fixed to the ski using the fixation member 106. Inan embodiment using the bushing 156, the fixation member 106 is fixed tothe ski using the bushing 156. The spring 108 is wind up by rotating thepivoting member 106 counterclockwise in the embodiment shown, as shownin FIG. 23. The pivoting member 106 is turned a predetermined number oftimes corresponding to the desired tension to be transferred to thespring. The stopper 144 is then installed to prevent the spring tounwind.

FIGS. 26a, 26b, 26.1a, 26.1b and 26.2a show another embodiment of ashaft 220 used with the first embodiment of the retractable wheel systemillustrated in FIG. 1. To pass from the retracted configuration to theextended configuration, the spring 8 rotates on its longitudinal axis,causing a small longitudinal elongation of the spring 8. Even if theelongation is small, the stress induced on the retaining ring 37 may beenough to dislodge it from the groove 245. The second embodiment of theshaft 220 provides a solution to this problem. The slot 233 isconfigured to receive the first extremity 28 of the spring 8. As shownin FIG. 26.2a , there is an angle π between the bottom 235 of the slotand the top 237 of the slot. The walls 239 and 241 are not at aperpendicular angle relatively to the surface 243 of the shaft. Thisconfiguration forces the first extremity 28 of the spring 8 to stay inthe bottom portion of the slot 233. It is to be noted that this shaftcould be use in other application such as with a transmission arm onwhich a spring is connected.

The angle π may vary between 8° and 15°, more preferably between 10° and14°. It has been found during experimentation that an angle of 12°provides better results.

The material of the parts of the retractable wheel system are resistantto impacts, winter conditions, principally. For example, the structureof the system may be made from composite, aluminium, steel, or otheralloys. The spring is typically made from steel. The case may be madefrom a variety of materials, for example composites, metal or metalalloy or from plastics. The case is preferably made from polyethylene(UHMW). The wheel is preferably made from a resilient material that isresistant to cold temperatures, as known in the art.

It is to be noted that the tension in the spring is not the same in theretracted configuration and in the extended configuration. Indeed, whenthe wheel is in an extended configuration, it induces a supplementarytension in the spring. In the retracted configuration, the tension is atleast sufficient to maintain the wheel in the retracted configuration.In the retracted configuration, the tension may be of 5 to 15 lbs forexample. In the extended position, the tension may go up to 15 to 20lbs.

It is to be noted that the different parts of the retractable wheelsystem may be unitary, or they may be assembled by using known means inthe art, such as welding, screws, rivets, etc. . . .

While illustrative and presently preferred embodiment(s) of theinvention have been described in detail hereinabove, it is to beunderstood that the inventive concepts may be otherwise variouslyembodied and employed and that the appended claims are intended to beconstrued to include such variations except insofar as limited by theprior art.

The invention claimed is:
 1. A shaft to be used with a spring comprisinga first and a second extremity, the shaft having an axis, wherein theshaft comprises: a) a first and a second extremity; b) a slot extendinginto one of the first and second extremities of the shaft, the slotcomprising a top portion and a bottom portion, the slot being configuredto receive the first extremity of the spring; wherein the slot isconfigured to force the first extremity of the spring towards the bottomportion of the slot when the spring is twisted to be tighter.
 2. A shaftas described in claim 1, wherein the slot extends substantially axially.3. A shaft as described in claim 2, wherein the bottom portion and thetop portion of the slot defines an angle therebetween.
 4. A shaft asdescribed in claim 3, wherein the spring is configured to be comprisedin a case.
 5. A shaft as described in claim 4, wherein the shaft isconfigured to be inserted in an adapter, wherein the adapter comprises agroove configured to receive the first extremity of the spring.
 6. Ashaft as described in claim 5, wherein the first extremity of the shaftis configured to be connected to a connector having a plurality ofholes, the connector configured to receive the second extremity of thespring.
 7. A shaft as described in claim 2, wherein the slot issubstantially perpendicular to the second extremity of the shaft.
 8. Anactuator for placing a snowmobile ski wheel in contact with a surface,wherein the actuator extends from a wheel shaft and is configured toplace the snowmobile ski wheel in contact with the surface, wherein theactuator is transverse to a ski.
 9. An actuator as described in claim 8,wherein the actuator is activated with a foot.
 10. An actuator asdescribed in claim 9, wherein the wheel is configured to adjust thedistance between bottom of the wheel and an undersurface of thesnowmobile ski.
 11. An actuator as described in claim 8, wherein theactuator extends outwardly from the wheel shaft.
 12. An actuator asdescribed in claim 8, wherein the actuator extends outside of and areadefined by a vertical projection along a perimeter of the ski.
 13. Anactuator as described in claim 8, wherein the actuator is parallel tothe wheel shaft.
 14. An actuator as described in claim 8, wherein theactuator has a longitudinal axis coaxial with a rotation axis of thewheel.
 15. A method to place a snowmobile ski wheel in contact with theground, wherein the method comprises the steps: a) to downwardly push onan actuating member extending from the wheel shaft with a sufficientforce allowing the wheel to be place in contact with the ground, theactuating member being transverse to a ski; and b) to maintain the wheelin contact with the ground using the weight of the snowmobile.
 16. Themethod to place a snowmobile ski wheel in contact with the ground asdescribed in claim 15, wherein the step to downwardly push on anactuating member produces sufficient force to overcome the resistance ofa shaft comprising a slot to be used with a spring configured to force afirst extremity of the spring towards the bottom portion of the slotwhen the spring is twisted to be tighter.
 17. The method to place asnowmobile ski wheel in contact with the ground as described in claim16, wherein the weight of the snowmobile produces a force greater thanthe tension in the spring.